This is a second feature from this patch that doesn't seem to have made it into the demo, the other being the poison patch (going to bump that thread again).Ultima Online Patch Notes for 04/13/1998
These are the official patch notes from the original release of Ultima Online. These patch notes were found at [1].
This update listing includes the contents of the mini-patch that went in on 4/20/98.
* You can no longer teleport with a teleporting object and stay invisible.
I am wondering if the demo did not contain this complete patch.